1. Field of the Invention
The invention relates to a reaming tool for reaming bone canals.
2. Description of the Related Art
Such reaming tools are applied in tubular bones, for example with the femur, for applying a hip joint prosthesis or before driving in a bone nail for the femur, tibia, humerus, etc. From EP 0 508 710 there is known a reaming tool which consists of a drill head and an elongate shank which can be connected thereto. The drill head consists of four teeth arranged at a 90xc2x0 distance with a chamfer which furthermore comprises a central through-bore. The shank, which is likewise drilled through has a smaller diameter than the drill head. The central through-bore of the shank and drill head serves for accommodating a guiding wire along which the reaming tool is driven forward.
From EP 0 440 377 there is further known a reaming tool which comprises a modified drill head and a shank which is formed flexibly. With the help of the flexible shank which at the same time represents a flexible shaft the drill head may also be moved along an arcuate path, which is required in many cases. For such a flexible shaft there are various known designs. They must not only be flexible but also be able to transmit a suitable torque.
On application, the chips removed away from the bone are conveyed behind the drill head into the intermediate space between the shank and the canal. With longer drillings it is therefore necessary to remove the tool from the canal from time to time in order to remove the chips. In this way the operating time is drastically increased. If the removal of the chips is not effected in time, a blockage of chips may occur with a corresponding blocking up of the drill head by which means an unallowable loading of the bone may occur, in particular by the developing heat.
It is therefore the object of the invention to provide a reaming tool for drilling bone canals with which the removal of chips is significantly improved.
This object is achieved by the device of the invention.
With the reaming tool according to the invention, the shank is at least over a part of its length spiraled in the manner of a thread. Preferably, the spiraling extends over the whole length of the shank, at least over a length such that the spiraled section is still located outside the bone when the drill head is in its furthest driven in position.
Although the outer diameter of the spiraled shank, for obvious reasons, is clearly smaller than the outer diameter of the drill head, it is possible with such a flexible shank to convey a sufficiently large part of the machined chips to the outside. Under certain circumstances all temporary removal of the drill head from the drilled out canal, for the purpose of chip removal, is done away with, however at least the number of such procedures is limited to a minimum.
In order to prevent damage to the canal walls, one form therefor of the invention provides for the thread tip to be flattened or rounded.
Although it is conceivable to form the shank of metal, it may be manufactured just as well from plastic.